This is the accepted version of the following article: Busia L, Schaffner CM, Aureli F. Relationship quality affects fission decisions in wild spider monkeys (Ateles geoffroyi). Ethology. 2017;00:1–7. https://doi.org/10.1111/eth.12609, which has been published in final form at http://dx.doi.org/10.1111/eth.12609